How much do you know about hair color and stem cells?

Study Notes

Certain stem cells, called melanocyte stem cells (McSCs), move between growth compartments in hair follicles to maintain hair color.
As people age, increasing numbers of McSCs get stuck in the stem cell compartment called the hair follicle bulge and lose their ability to mature and maintain hair color.
The researchers found that McSCs transform between their most primitive stem cell state and the next stage of their maturation, the transit-amplifying state, and depending on their location.
McSC plasticity is not present in other self-regenerating stem cells, such as those making up the hair follicle itself.
WNT signaling is needed to stimulate the McSCs to mature and produce pigment.
The number of hair follicles with McSCs lodged in the follicle bulge increased from 15% before aging to nearly half after forced aging.
The stuck McSCs ceased their regenerative behavior as they were no longer exposed to much WNT signaling and hence their ability to produce pigment in new hair follicles, which continued to grow.
Other McSCs that continued to move back and forth between the follicle bulge and hair germ retained their ability to regenerate as McSCs, mature into melanocytes, and produce pigment over the entire study period of two years.
The loss of chameleon-like function in melanocyte stem cells may be responsible for graying and loss of hair color.
The researchers plan to investigate means of restoring motility of McSCs or of physically moving them back to their germ compartment, where they can produce pigment.